Thus the distance between New York and Oporto, following the former (great circle sailing), amounts to 3000 m., while following the rhumb, as in Mercator sailing, it would amount to 3120 m.
By this time, French armies, to a great extent controlled by Napoleon from a distance, had advanced - Soult from Galicia to capture Oporto and Lisbon (with General Lapisse from Salamanca moving on his left towards Abrantes) and Marshal Victor, still farther.
Soult (over 20,000), leaving Ney in Galicia, had taken and sacked Oporto (March 29, 1809); but the Portuguese having closed upon his rear and occupied Vigo, he halted, detaching a force to Amarante to keep open the road to Braganza and asked for reinforcements.
Soult Passage of expected the passage of the Douro to be attempted the Douro, near its mouth, with fishing craft; but Wellesley, by May 12,1809, a daring surprise, crossed (May 12) close above Oporto, and also by a ford higher up. After some fighting Oporto was taken, and Soult driven back.
The stirring incidents in the political emancipation of Portugal inspired his muse, and he describes the bitterness of exile, the adventurous expedition to Terceira, the heroic defence of Oporto, and the final combats of liberty.